


the perils of (accidentally) turning into a cat

by fluffysfics



Category: Doctor Who (2005)
Genre: Canon Divergent, Cheetah Virus, F/M, Fluff, Post-Episode: s12e10 The Timeless Children, cat-related humour, dubious pathological science, the Doctor is a mad scientist, the Master suffers but like...in a fun way
Language: English
Status: Completed
Published: 2020-07-27
Updated: 2020-07-27
Packaged: 2021-03-06 01:48:33
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,206
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25555345
Author URL: https://archiveofourown.org/users/fluffysfics/pseuds/fluffysfics
Summary: The Master wakes up one morning, and discovers that he has fangs. Obviously, this isn’t ideal.The Doctor agrees to help- for the small price of...his dignity.
Relationships: Thirteenth Doctor/The Master (Dhawan)
Comments: 5
Kudos: 59





	the perils of (accidentally) turning into a cat

The Master knew that something was wrong when he woke himself up by biting through his lower lip. 

The pain was sharp enough to make him jolt upright, and immediately he was aware of several things. Well- several _dozen_ things, through bizarrely heightened senses, which was strange enough in itself. But a few things were particularly important. 

Firstly, he could taste the blood on his lip far more sharply than usual. Secondly, when he ran his tongue over the wound, it was _rough_. And finally, perhaps most damningly- when he lifted his hand to touch his lip, his fingernails were dark and wickedly curved. Claws. 

Oh, come _on_. It had been _years_. How long did this thing _last_?

He scrambled out of bed, pulling on a shirt and trousers. The trousers were fine- the shirt took a little more time than usual, because his damn claws kept snagging on the buttons and almost wrenching them off. As soon as it was on, he bolted out of the room and ran off in search of the Doctor. 

It took a _considerable_ amount of effort not to run to her on all fours. 

She’d been working in one of her absolutely chaotic laboratories when he’d left her to go take a nap, and she was probably still there now. She could stay in those rooms for days, focusing on her latest weird project. The Master sniffed the air- he could _sense_ her, not all that far away. 

Shoving open the door, he strode over to the Doctor, planting his newly-clawed hands on the workbench in front of her. 

“Doctor. A _thing_ has- unfortunately- happened.” 

That got her to look up. She put down the blender she’d been tinkering with, lifting up her goggles and squinting at him. 

“...Your eyes are yellow, Kosch.” 

They were? Oh, great. He scowled, and the Doctor stared at him even more. 

“Oh! You’ve got fangs! And- your hands- claws! Ohh, this is- fascinating! Brilliant!” She practically skipped around to his side of the bench, grabbing one of his hands, poking at his lip to expose the fangs. 

If she’d been anyone else, the Master wouldn’t have hesitated to bite several holes in her nosy hands, since he was clearly capable of that now. As it was, he just sighed heavily and let her get the excitement out of her system. 

Eventually she let go of him, and stepped back a little, and made an _attempt_ to look solemn. It didn’t work very well. She still couldn’t hold back a grin. 

“So. Cheetah virus came back,” she said, as casually as if they were chatting about the weather. 

“Apparently.” The Master folded his arms. “We’re in _your_ lab, dear. Can you get a move on and fix it?” 

“Fix it?” She looked offended at the very thought, reaching out to prod lightly at a claw and then jump back again with a grin when he flexed them at her. “We don’t even know what caused it! You been petting any cats lately?”

“Where would I have found _cats_? I haven’t left your ship.” 

“One mighta snuck in. They’re very sneaky creatures, cats.” The Doctor turned away, rooting through the mess on her workbench in search of something. “Hmm. What’s changed, what’s- oh! The Cyberium!”

“You got rid of that,” the Master reminded her. After a week and a half of incredibly delicate fiddling around, the Doctor had finally been successful in getting the damn thing out of his head yesterday. It was currently sitting in a jar in his bedroom, like the world’s angriest lava lamp. He liked to watch it swirl, and occasionally mock it. It didn’t appreciate that. 

“Yeah,” she said. “ _Yesterday_. And then you get all sleepy and go take a nap, and you come back like this!”

“Most people get sleepy sometimes, Doctor,” he pointed out, but she was on a roll and completely ignored him. He wondered when the last time _she’d_ slept was. 

“So...we get the Cyberium out. It leaves your head all scrambled up-“

“It did not!”

“Did too,” she retorted. “You called me Ushas _twice_ yesterday. She’d set a dinosaur on you if she knew. Anyway. It leaves your head all scrambled up. Like...your mental immune system’s gone all fuzzy for a bit. And we both know you can’t cure cheetah virus, it just goes dormant. So you go to sleep, and the virus takes its chance and gets you! And now you’re a kitty!”

“I am not _a kitty,_ ” the Master said, with as much disdain as he could muster. _Kitty_ was a very hard word to say in anger, and it was made even more difficult by the fact that the Doctor’s theory was probably correct. 

She beamed at him, and then stuck a needle in his arm. 

“Ow!” To his credit, he at least managed to control a frankly embarrassing urge to hiss and jump onto the table. 

“Just need some blood,” she explained cheerily. “Then the TARDIS can sort you out a treatment. Won’t be permanent, it could come back at any time. But hey, that’s fine. I like cats.” 

“I am not a cat- _ow_.” The Doctor pulled the needle out again, and hurried over to go stick the blood in a scanner. For someone named after a medical professional, she had absolutely no bedside manners whatsoever. 

The Master sighed, tapping his claws on the bench as he waited. It had been so long since he’d last dealt with the cheetah virus. He actually quite liked the claws, when you got past how annoying they were for doing small tasks. And the fangs were pleasantly intimidating. The yellow eyes he apparently had were less nice, though. He liked the big soulful brown ones he’d ended up with this time. 

“Right.” The Doctor hurried back over to him. “TARDIS is working on a treatment plan. We’ll get you all sorted out soon.” 

“Good.” The Master stepped closer, leaning in to steal a grateful kiss, but she ducked away. 

“Ooh. Watch the fangs. Don’t know how I feel about those,” the Doctor said. She caught hold of the front of his shirt so he couldn’t pull back, and started squinting into his mouth. 

“I’ll bite your nose,” he threatened. 

Unperturbed, the Doctor continued her examination, and then finally (carefully) kissed him, holding onto his shirt until she eventually saw fit to release him. 

“You’ve got a cheetah tongue, too,” she said, grinning. “That’s fun.” 

“Is it?” The Doctor was enjoying this far too much, he decided. It was a shame that her happiness was absolutely endearing, or else he might have been tempted to spoil it a bit. Actually bite her, or something. 

“Well. Could be. Lot of things could be fun about this.” She perched herself on the edge of the bench, looking as innocent as could be. “Could get you a collar and make you play fetch in a park.” 

“That’s _dogs_ ,” the Master said back quickly. Slightly too fast. He felt himself blush, and hoped very much that his skin was dark enough to hide it. 

“Some humans take their cats for walks,” the Doctor insisted. 

“That’s just- ridiculous! Undignified. _Completely_ unnecessary. And anyway, I’m _not_ a cat,” he said, glaring at her in an incredibly catlike sort of way. 

“Sure you’re not,” she said, dropping him a conspiratorial wink and jumping back off of the bench. The Master hissed at her retreating back, and then caught himself and stopped abruptly. Ugh, it was getting _worse_. But- _really_. Comparing him to a common house cat. At the most, he was maybe half- _cheetah_ , definitely not a cat, and just as regal and majestic as the real thing. 

The Doctor fiddled with her scanner for a minute, and he watched. At one point, the machine sparked, and she just smacked the side of it and told it to _shh_. Eventually, it spat out a small bottle. 

“Pills,” she announced, throwing the bottle at him. His reflexes were good even without the cheetah virus aiding him, so the Master caught it without a problem. The child-safe lid, however, took rather more wrangling. Damn claws. 

“Take one of those, once an hour, for, um...fourteen hours. That should do it,” the Doctor explained, taking the bottle from him and uncapping it with a grin. “How’d you get cats to take their medicine? Hide it in peanut butter?” 

“That’s dogs again,” the Master said, giving her a withering look and swallowing one of the pills. “How long until all of _this_ goes away?” He waved vaguely at his face and hands. 

“Fourteen hours,” the Doctor said, far too gleefully. “Won’t fade until all of the virus has been pushed back into a dormant state. Sorry.” 

“You’re not sorry,” the Master grumbled, shoving the pill bottle into his pocket. 

“No,” she agreed. “I’m not. You _sure_ I can’t play fetch with you?” 

“Very sure,” he snarled, showing off two sharp fangs that would decimate any balls she tried to throw for him. 

“Bad kitty,” the Doctor said, rummaging on her workbench and then pointing at him threateningly with a partially disassembled blender. “No threatening me.” 

“You’re threatening _me_ , with that,” he argued. 

“Am not! Just needed something to point.” She dropped the blender again, darting closer to him until she was thoroughly inside his personal space. “So. Your cat traits...”

“ _Cheetah_ traits.” 

“Cat traits,” she continued innocently. “There’s the obvious ones, all of the things I can see. But is there anything _else_?” 

“Sharpened senses,” the Master began, figuring that if he played along with her then maybe she’d get bored faster and stop prodding him. “Slightly altered vocal cords. I think.” He certainly couldn’t hiss like that normally, at least. 

“Yeah, yeah. Not what I meant.” And with that, the Doctor reached up, scratching behind his ear with blunt nails. 

His first instinct, the Koschei-the-Time-Lord instinct, was to scowl at her and pull away. But it was swiftly overridden by the Koschei-the-cheetah instinct, which was apparently to do quite the opposite. 

He leaned into her hand, and _purred_. That _definitely_ wasn’t a noise he was usually capable of making. 

The Doctor gasped delightedly, scratching harder. To the Master’s annoyance, that only increased the volume of the purring. Then again, he wasn’t _really_ annoyed. It felt _good_. 

“Well,” she said, pulling her hand away after a minute. “That’s fun.” 

“For you, maybe.” 

“Yeah, yeah. Grumpy kitty. I _know_ you like it too, you were the one _purring_.” 

The Master glared at her, but it was very hard to tell her she was wrong when she wasn’t. And it was made even harder by the feline urge to butt his head against her hand until she started scratching him again. He was drawing a line there, that sort of behaviour was _way_ too far. 

“Bet I know a good way to pass fourteen hours,” the Doctor said, grinning. 

“Let me guess. You want to humiliate me even more,” he said, raising an eyebrow. 

“If you want to call it that,” she said lightly. “You’ll _enjoy_ it. Promise. You’re such a pretty kitty when you smile...” She seemed delighted by the rhyme, mouthing the words ‘pretty kitty’ to herself a few more times. 

“I’m not pretty. _Or_ a kitty. As you well know.” 

“Yeah, but I like teasing you. Your ears twitch whenever you get irritated like this.” 

Did they? The Master immediately clamped his hands over them, pulling a face when he felt them flick slightly back and forth. 

The Doctor burst out laughing, and leaned in to kiss him, patting his cheek with a fond smile. “C’mon, Kosch. You’re stuck with this for a bit, might as well enjoy yourself. Bedroom. We can lie down, I can scritch your head for you, you can try and talk and end up purring...” 

“I’ll bite your hand if you keep teasing me like that.” 

“No you won’t.” She was right, probably. “C’mon! Agree with me. It’ll be fun. And it’s only fourteen hours.” 

The Master sighed. Fourteen hours with the Doctor, being _petted_ , or fourteen hours sitting in his own room, resisting the urges to hunt things, or eat raw meat, or _lick himself_. Ugh. Put like that, he supposed there was an obvious choice. 

“Fine,” he said, trying to look more grudging about it than he felt. 

The Doctor beamed at him, a smile so infectious that one pulled at his own lips, too. “Perfect. _Good_ kitty.” 

The Master had a feeling that the _kitty_ thing was going to stick around for a while. Oh well. She’d called him worse before. He let her pull him into another kiss, and then she grabbed his hand and dragged him off towards her bedroom. 

She was rambling about various things she wanted to try on him, but the Master figured that it was probably safest not to listen. He just squeezed the Doctor’s hand, careful not to let his claws dig into her skin, and followed her. It was nice to see her so happy, so enthusiastic, even if the reason _why_ was a little...unfortunate. 

He could take a few hours of cheetah-related experimenting if it meant getting to see her smile, though. Any day. 

**Author's Note:**

> been a while since I posted so- have some fluff!! might be posting a bit less often for the next month or so because I’m writing fics for a gift exchange, but There Will Be Some Content, I promise!
> 
> hope you enjoyed! comments and kudos are appreciated as always <3


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